The present invention relates to microphones, including MEMS microphones. FIG. 1 illustrates a conventional MEMS microphone 100. The MEMS microphone 100 includes a movable electrode 105 (i.e., membrane) having a first side 107 and a second side 108, a stationary electrode 110, and a barrier 120. The barrier 120 isolates a first side 125 and a second side 130 of the MEMS microphone 100. Acoustic pressures acting on the first side 107 and the second side 108 of the movable electrode 105 cause movement of the movable electrode 105 in the directions of arrow 145 and 150. Movement of the movable electrode 105 relative to the stationary electrode 110 causes changes in a voltage difference between the movable electrode 105 and the stationary electrode 110. As is known, ambient pressure also acts on the first side 107 and the second side of the movable electrode 105. Further, the movement of the movable electrode 105 is also based on the ambient pressure acting on the movable electrode 105. Although the ambient pressure changes based ambient conditions (e.g., altitude, wind, humidity, etc.), the remaining discussion is focused on acoustic pressures acting on the movable membrane 105.
MEMS microphones 100, such as illustrated in FIG. 1, based purely on mechanical parameters are fixed in their response. FIG. 2 is a graph 200 of an exemplary frequency response 205 of the MEMS microphone 100 illustrated in FIG. 1. The horizontal axis is frequency (in hertz) and the vertical axis is gain (in dB).